The major variables affecting the outcome of allogeneic transplant include: patient selection (age and comorbidities); disease status at the time of transplantation (remission vs. active disease); type of donor (HLA matched vs. mismatched or related vs. unrelated); type of conditioning regimen; source of stem cells (bone marrow vs. peripheral blood). Recent advances in the field of stem cell transplant have substantially lowered transplant related morbidity and mortality.